1. Field of the Invention
This invention relates to a two-cycle internal combustion engine, and more particularly to an improvement in a combustion chamber of a two-cycle internal combustion engine.
2. Description of the Prior Art
In general, a two-cycle internal combustion engine which is conventionally known in the art is typically constructed as shown in FIG. 1. More particularly, it includes a cylinder 10 having a side wall 12 formed with a plurality of opening or scavenging ports 14, a piston 16 vertically movably arranged in the cylinder 10 and a cylinder head 18 for closing an upper opening 20 of the cylinder 10. The so-arranged cylinder 10, piston 16 and cylinder head 18 cooperate together to form a combustion chamber 22. The cylinder head 18 comprises an upper section 24 of a dome-like shape formed therein with a space or top chamber 26 of a substantially hemispherical shape and a lower section 28 of a flat cylindrical shape communicated to a lower end of the upper dome-like section 24 and formed so as to serve as a lower flange of the upper dome-like section 24. The lower flat cylindrical section 28 is formed with a space or chamber 30 of a substantially frust-conical shape which is communicated with the top chamber 26 of the upper dome-like section 24 through a circumferential border 31 defined therebetween and serves as a squish chamber. The upper dome-like section 24 and lower flat cylindrical section 28 are formed integral each other. The internal combustion engine also includes an ignition plug 32 threadedly inserted through an upper portion of the upper dome-like section 24 so that its tip end 34 is positioned at a substantially central portion of the top chamber 26. The side wall 12 of the cylinder 10 is also formed with a discharge port 34 through which combustion gas is exhausted.
Unfortunately, the so-constructed conventional two-cycle internal combustion engine exhibits a disadvantage of failing to form a vortex flow of fuel gas in proximity to the tip end 34 of the ignition plug 32, resulting in a failure in an improvement of ignition performance of the engine, because the tip end is positioned at a substantially central portion of the top chamber 26 and fuel gas is merely forcedly fed through the squish chamber 30 to the top chamber 26 while being compressed before the piston 16 reaches a top dead center. This also leads to consumption of much fuel.
Further, when the ignition plug 32 ignites fuel gas in the top chamber 26, a flame of the fuel gas is propagated toward the piston 16 at a high velocity to cause pressure in the combustion chamber 22 to be rapidly increased, resulting in large impulse force being exerted on a head surface 38 of the piston 16, an inner surface 40 of the lower flat cylindrical section 28 defining the squish chamber 30 of the cylinder head 18, an inner surface 42 of the upper dome-like section 24 defining the top chamber 26 of the cylinder head 18 and the like, so that vibration occur at the piston 16, cylinder head 18 and cylinder 10 to cause resonance, resulting in noise. In order to eliminate such a problem, it is attempted to form the top chamber 26 into a large depth to increase a distance from a position of ignition of fuel gas by the ignition plug 32 to the squish chamber 30, to thereby lengthen a time required for propagation of a flame. Unfortunately, such an approach fails to cause a sufficient amount of fuel gas to be present at the ignition position to deteriorate ignition performance of the engine, resulting in an output of the engine being decreased and much fuel being consumed. Also, this renders clarification of exhaust gas difficult.